Vector leptoquarks beyond tree level. III. Vectorlike fermions and flavor-changing transitions
Javier Fuentes-Martín, Gino Isidori, Matthias König, Nudžeim Selimović
Abstract
Extending previous work on this subject, we evaluate the impact of vectorlike fermions at next-to-leading order accuracy in models with a massive vector leptoquark embedded in the $SU(4)\ifmmode\times\else\texttimes\fi{}SU(3{)}^{\ensuremath{'}}\ifmmode\times\else\texttimes\fi{}SU(2{)}_{L}\ifmmode\times\else\texttimes\fi{}U(1{)}_{X}$ gauge group. Vectorlike fermions induce new sources of flavor symmetry breaking, resulting in tree-level flavor-changing couplings for the leptoquark not present in the minimal version of the model. These, in turn, lead to a series of nonvanishing flavor-changing neutral-current amplitudes at the loop level. We systematically analyze these effects in semileptonic, dipole and $\mathrm{\ensuremath{\Delta}}F=2$ operators. The impact of these corrections in $b\ensuremath{\rightarrow}s\ensuremath{\nu}\ensuremath{\nu}$ and $b\ensuremath{\rightarrow}c\ensuremath{\tau}\ensuremath{\nu}$ observables are discussed in detail. In particular, we show that, in the parameter region providing a good fit to the $B$-physics anomalies, the model predicts a 10% to 50% enhancement of $\mathcal{B}(B\ensuremath{\rightarrow}{K}^{(*)}\ensuremath{\nu}\ensuremath{\nu})$.